7+ Randomly says ‘No service’ ‘searching’ in fully covered areas

My phone will randomly say ‘searching’ ‘no service’ or say I’m connected to service but neither my cellular data, calls or texts work. I’m with boost mobile and am currently on one of their unltd $30 or something like that and it has been paid for and up to date! Works fine connecting to wifi and Bluetooth. Maybe problem with mother board?

It’s the most expensive phone I’ve ever bought and it’s really getting under my skin that it’s not working! Cheers for your help!